A prosthetic foot that mimics the human foot in function is disclosed. The prosthetic foot has hindfoot triplanar motion capability, biplanar midfoot and forefoot motion capabilities and high low dynamic response characteristics for improving gait and comfort qualities of the amputee in walking, running and jumping activities.
Those in the field of prosthetics have in the past manufactured prosthetic feet which permit varying degrees of motion capability. Most of the known prosthetic feet utilize metal hinges with rubber bumpers to enable this motion capability. These components are sources for mechanical failures and wear. The known prosthetic feet are also generally expensive to produce and maintain. None of the conventional prosthetic feet mimic human gait characteristics, e.g., while known designs allow some motion capability, the conventional prosthetic feet do not reflect humanoid characteristics. These characteristics relate to the biomechanical function of the human foot and ankle joint in gait. The prior art prosthetic feet have not achieved true human gait characteristics because their design features do not mimic the human foot.
The human foot is a complex comprised of twenty-six separate bones. The bones of the foot articulate with one another to create joints. The joints of the foot, through these articulations, allow movement to occur. The motion capability of a particular joint is dependent upon bony articulations, ligamentous reinforcements and muscular control. Motion capability of specific joints of the foot has been studied quite extensively through history. These scientific studies have identified fourteen different axes of rotations of all the joints of the human foot. They have through thoughtful analysis determined how these axes of rotations and motion capabilities function in human gait and running and jumping activities. The prosthetic foot of the present invention has been made in light of these scientific studies with a view toward providing an improved prosthetic foot that mimics the human foot in function in order to provide the amputee with normal human gait characteristics and improve the quality of life of the amputee.
A prosthetic foot according to the present invention comprises a forefoot portion, a midfoot portion and a hindfoot portion, wherein the hindfoot portion includes first and second joints permitting closed kinetic chain motion of the prosthetic foot in gait. The first joint has a joint axis oriented for permitting motion of the hindfoot portion about the first joint axis which is at least primarily in the sagittal plane. The second joint has a joint axis oriented for permitting motion of the hindfoot portion about the second joint axis which is at least primarily in the frontal and transverse planes. In the disclosed, preferred embodiment, the first and second joints are formed integrally with the hindfoot portion by respective struts of resilient material of the hindfoot portion. More particularly, the forefoot, midfoot and hindfoot portions of the prosthetic foot are formed of a single piece of plastic as by molding and/or machining. The first joint in the hindfoot portion mimics an ankle joint and the second joint mimics a subtalar joint to allow the foot to function like a normal foot.
The subtalar joint in the hindfoot portion of the disclosed embodiment constitutes a means for permitting triplanar closed kinetic chain motion of the prosthetic foot in gait. This triplanar motion capability improves the foot staying plantar grade during the stance phase of gait. It also decreases residual limb to socket shear forces associated with motion in the transverse plane.
The plantar surface of the midfoot portion has a longitudinal arch which is formed with a concavity having a longitudinal axis that is deviated in the frontal plane 25xc2x0-42xc2x0 from the transverse plane to create frontal and sagittal plane motion capabilities. The medial aspect of the longitudinal arch concavity is larger in radius and more proximal than the lateral aspect of the concavity. The longitudinal arch is shaped to create a high low dynamic response capability of the foot in gait such that the medial aspect of the longitudinal arch has a relatively higher dynamic response capability and the lateral aspect of the longitudinal arch has a relatively lower dynamic response capability.
The posterior of the forefoot portion of the prosthetic foot includes at least one expansion joint hole extending through the forefoot portion between dorsal and plantar surfaces thereof. An expansion joint extends forward from the expansion joint hole to the anterior edge of the forefoot portion to form plural expansion struts which create improved biplanar motion capability of the forefoot portion. Concavities and convexities are utilized on surface areas of the one piece body of the prosthetic foot with the longitudinal axis orientations thereof being selected to create dynamic response and motion capabilities which mimic the human foot.
These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the disclosed, preferred embodiment, taken with the accompanying drawings.
The foregoing and a better understanding of the present invention will become apparent from the following detailed description of an example embodiment and the claims when read in connection with the accompanying drawings, all forming a part of the disclosure of this invention. While the foregoing and following written and illustrated disclosure focuses on an example embodiment of the invention, it should be clearly understood that the same is by way of illustration and example only and the invention is not limited thereto. The spirit and scope of the present invention are limited only by the terms of the appended claims.